A NOTE ON THE SKELETONS OF TWO ALASKAN 

 PORPOISES 



By GERRIT S. MILLER, JR. 



curator, division of mammals, u. s. national museum 



(With One Plate) 



Skeletons of two Alaskan porpoises, Phoccena phococna (Linnaeus) 

 and Phocoonoidcs dalli (True), have recently been mounted in the 

 United States National Museum. Before these skeletons were placed 

 on exhibition the photographs were made that are reproduced on the 

 plate accompanying this article. 



In his original account of Plwarnoidcs (Bull. Amer. Mus. Nat. 

 Hist., Vol. 30, pp. 31-50, May 16, 191 1) Andrews figured the 

 skull, jaw, hyoids, sternum, scapula, flipper, and several vertebrae; 

 but these individual parts fail to give an adequate idea of the striking 

 peculiarities of the genus as compared with its relative PJioccena. 

 Chief among these peculiarities are the length and slenderness of the 

 chevron bones, of the ribs (length of longest rib contained about 

 4^ times in length of vertebral series, as compared with 5-| times in 

 Phoccena) , and of the dorsal spines (longest spines contained about 

 loj instead of 17-J times in length of vertebral series) ; the shortness 

 (or compression) of the vertebral centra by virtue of which the 45 

 centra of the dorso-lumbar series are crowded into appreciably less 

 space than that occupied by only 29 dorso-lumbar centra in Phoccena. 

 Particularly noticeable also are the differences in form of the scapula, 

 arm and hand. 



In the great height of the dorsal spines and the compression of the 

 centra Phococnoidcs appears to be unique among living members of 

 the family Delphinidse. There is no approach to these conditions in 

 the genus Neomeris. 



The two skeletons, as mounted, are of the same length, 1,760 cm. 

 In the Phoccena the depth of chest, including vertebral spines, is about 

 30 cm., while in the Phocccnoides it is about 44 cm. 



Considering the peculiarities of the skeletons, the skulls of Phoccena 

 and Phocccnoides are remarkably alike. In the teeth and gums, how- 

 ever, the differences are pronounced.* 



'See Miller, Proc. U. S. Nat. Mus., Vol. 74, .Art. 26, pp. 1-4, pis. 1-4, 

 January 26, 1929. 



Smithsonian Miscellaneous Collections, Vol. 82, No. 13. 



